DC Generators or AC ?

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Shove

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Hi
We are looking to fit a generator to our 45ft cruiser (bluewater sailing in mind). I'm only familiar with the conventional 230v AC types - 4.5kva etc. On visiting the boat show I understand Mastervolt, Onan & Northern Lights are amongst the best. I should point out that all 230V sockets and hard wired appliances will be supplied by a 2500kw inverter. (could be bigger as yet this is not fitted)

However I got chatting on the Fischer Panda stand and they suggest we consider fitting a 12/24v DC generator. I understand the theory is that as each appliance is utilised (for example: freezer, Hot water, AC sockets, hair dryers, charging etc) the Genny will auto start to keep the battery bank topped up to the required level for the inverter to work.

The positives being:
- lighter unit
- power on demand and not running unnessarily
- lower hours
- lower operating rpm

If you have any experience or thoughts on the above i'd really appreciate your advice /forums/images/graemlins/ooo.gif

Al
 
power losses on an inverter are in the region of 20%. I'd go for a 240v genny and omit the inverter. Saves on complicated wiring too, and having a battery bank that takes a caning whenever you use the kettle.
 
You would be better off looking at the Liveaboard Forum than these armchair critics!!! Search the archives and find people who have actually used a 12v system.

We have a Fischer Panda 12v genny with a 2.5KVA inverter. The advantages are numerous as you suggest, but let me briefly add a few comments.

They are much quieter because they run at the speed dictated by the charge required - an AC genny always runs at the same speed, hence the maintenaince on 12v is less. Ours is under the bed and very well insulated, so that we can have it running and when we are in the saloon it just sounds like a water pipe huming.

A very large charging current, ours gives 250 amps or more, so battery charging is much quicker. An AC genny will only drive your shorepower charger to deliver whatever amps that is designed for. Why make 240 volts ac to charge a 12v battery?

With a decent sized battery bank then AC is available all the time to run anything via the batteries. No need to start the genny. Don't leave the genny on auto start 'cos it will probable start when you put on a heavy load. It also says in the manual have all the electrical circuits off when you start to avoid spikes possibly damaging equipment. We only use auto start when the batteries are low and need charging, only then does auto stop work. You can't manual start and auto stop!!!

With larger inverters and larger battery banks the 12 volt option is becoming more and more popular - but sometimes a little difficult for some people to get their heads around.
 
Thanks Leg420 - its good to hear of personal experience. Do you also have a conventional Battery charger fitted to the boat for when your plugged into shore power?

Would you reccommend any other systems other than the Fischer Panda unit? I've seen another unit called a WhisperGen which makes good reading.
Out of interest, other than your engine starter battery, what's your total ah battery supply?

cheers
Al

Will have a look at the liveaboard forum too
 
My Inverter is also my battery charger. The Victron multiplus is a great unit which sits in series with the shorepower AC and either provides AC or charges the batteries - or both at the same time. It also supplements the shorepower - so if the shorepower breakers are set to 6 amps - set the Victron to 6 amps and if you want more AC it takes it from the battery. When the AC load goes below 6 amps its charges the battery. (Max 120 amps.)

Our house bank is 1050 Ah Lifeline AGMs - what the services and RNLI use, and not that expensive. They can take as much current as you can throw at them so even a smaller bank could cope with the 250 amps from the genset.

The Whispergen was something I looked at carefully - but you need to look carefully. I can't remember what the downside was but I rejected it bigtime. I think it was mainly a heatsorce, and not much battery charging, but I can't get their site to give me any info!!!

Lots of people have critised Fischer Panda - mainly their AC gensets, but I am pleased with mine. I managed to instal it myself and save £1500!
 
[ QUOTE ]
Hi
... I should point out that all 230V sockets and hard wired appliances will be supplied by a 2500kw inverter. (could be bigger as yet this is not fitted)



[/ QUOTE ]

Why do you need a two-and-a-half Megawatt inverter? /forums/images/graemlins/confused.gif
 
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